How to cut Threads on a tube

hey guys welcome back to metal tips and tricks my name is Dale I've got an interesting repair job here it is an airgun where the end the threaded end has broke off and it needs to of course be repaired now I'm showing you this video to show you the different challenges in turning down tubing and threading it as you can see here this is a very fine thread it's actually the thread pitch is 32 and it's got its challenges to thread something that fine on such a large diameter this is 3/4 inch aluminum stock I want to teach you the challenges that go on with turning aluminum especially tubing like this that's thin wall so if you look at tubing its biggest challenges it's very flexible and can go in any direction we were to let's say hold this in a three jaw Chuck well what happens we get three points and we end up just making a triangle and that's not going to be round and with this fine pitch thread if we're off too much it's not going to be a good fit if I go over the square if I go on the four jaw Chuck it's going to basically turn this into a square so you realize that clamping down onto aluminum is very challenging so what we're going to do is we're going to go in and use a collet and this one here is a 2 J collet what's great about a collet is when it tightens down on the material it tightens down equally on all sides of it so let me get this installed I'm going to let this tubing hang out a little bit further than I normally would and the reason for that is for camera angles with aluminum or any type of tubing it can always be off and out of round so we need to first check it to see how it is and we're just going to simply come in here with a dial let's check how it is okay so this is a one thousandth indicator point zero zero one and it's about 2,000 s out that's not bad that's very usable but let's say if it was out further than that how do you correct it well I want to show you that first thing what we want to do is we're going to lightly run a file over the top of it just to clean it up and I wanted to just get the high points off and that probably brought it in within tolerance just by filing it but let's say if it was squished and a little out of round what we can do is go in with a ball bearing like this it's very similar to metal spinning if you've never seen metal spinning you want to go do a search on it in YouTube and see what it is but hold on wait until I'm done doing this video first so it's simply what you want to do is just put a bearing on a shaft like this bring it in now I would normally square up the bearing but to save time I'm not going to do that and we're in pretty good and we want to of course get the bearing approximately in center with the tubing but it really doesn't matter and you would just simply turn on the lathe and as it's going around and it's oblong this will pick up and hit those high spots and start pushing it back in and back into place if your tubing is really far out it may not work but it's also one of those tricks you have to try it and find out first let me put the cutter back in I've already set up the cutter for this and it's an insert and what's great about insert especially for something like this is it's ground to a very fine point something that I don't think I really have well I could do it but it's a lot of work and it's just easier to go with an insert that has an accurately ground fine point to it now I'm not going to go over this whole transmission and how to set it up it's a little complicated and since a lot of people don't have a lathe like this I don't think you're going to really benefit and that's not the goal of this videos to show you how to thread but how to think about threading an aluminum tube like this so we're going to bring this around we're going to set a zero when I set up for zero here I make sure the handle is top dead center and the reason I do that is I know exactly where it is when I'm turning it so when I bring it down I just know I have to bring this up the top and look for zero boom I'm done very quick and easy now we're going to set up here for a scratch pass I've already set the compound to around 30 degrees so I'm going to come in here just kind of twist it around I hear it scratch and there we go set this dial to zero and come out now we're first pass we're going to do is what we call is a scratch pass and that's to make sure we have the transmission or your gearbox set up correctly so with this pitch gauge I'm going to check to make sure we're lined up pretty good now if I didn't have a pitch gauge I can go in with some material that's already been cut or you guys going to like this you can actually just go in with a tap and check it with that as long as it's a tap with a 32 pitch I'm going to back off the main cross slide bring it over bring the cloth cross slide back to zero again with this handle on top and when I engage here on this dial what's great about even numbers any knotch on that dial I can connect to it doesn't matter if it's a 1 2 or 4 or 3 or any of the half notches because it is an even number thread I'm going to go in five thousands for each cut now if you'll notice a tapered coming out because I don't want a weak spot on the on the threads like there was before so at this point I want to come in with the micrometer and this is a threading micrometer very cool very easy to use compared to using the wire system and the wire system is you set up three wires and you measure the distances between the wires and then do a calculation and blah-blah-blah-blah-blah bottom line is takes a lot of time here I need just come in the hardest thing I have to do is get it lined up square and into the right threads and the right grooves so the measurement that I am after is 0.72 5 and we have about thirteen thousand more to go make sure this one's at zero come into here said 13 let's go another 5,000 here test it I know people think that threading is rocket science and really the only way to know how to do threading is to practice literally I don't care if you don't have a project to work on just start just get some material out and practice find out how everything works and just keep doing it and the day that you need to do it you'll be ready to go let's do another measurement so it looks like I have another 5,000 to go but before I do that let's test the handle make sure it doesn't thread on it's a little tight I think what we'll do is go for a scratch pass and a scratch past is literally letting going back to your original settings your last cut and just let it pass through and clean it up now the very heavy scratch pass I think we might be there let's clean up with a wire brush paper the end done I think that is a really great repair some of the surprise on this way how much the scratch pass took off each time and I think I know what's going on here this lathe is really ready for a full tear down and rebuild on the compound slides and I think I'm gonna have to do a video on that I mean it'll be very interesting to show you what I do to a late to actually get up and running because the only thing I've done with this light since I bought it was make sure that it's dead-on level but I can see that the challenges I was having here that it was off a little bit and I think it's important for you to see that even a big machine like this can be not working correctly and I think it's great for you guys to see a machine that isn't cutting 100% correct so I'm going to work on setting up a video for you guys to show you how to set up a lathe and I sorry it's going to be a long video so it's going to probably broken up into multiple parts but this is how you turn down tubing remember you want to make sure that when it's clamped down that it stays round and that's the real key so if you guys like this type of video give me some thumbs up also give me some of your great comments I'd love to hear from you guys and also I want to back up just a second is I've been producing a video on Wednesday that I call QA and it's usually based on what video like this one here is done on Friday next Wednesday I'll have a QA for this turning so if you've got any questions please leave a comment I'll hopefully get to read it on QA alright guys until next time go out in your shop build something cool thanks

Channel: Build Something Cool

Views: 97,281

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Id: Ia_-sj23Fb0

Length: 13min 30sec (810 seconds)

Published: Sat Jan 23 2016